This post will demonstrate how to upload files to ActiveAdmin.

Source code can be found here

It is expected that you follow the "Getting Started" section from my previous post "ActiveAdmin With Ruby On Rails 7" (but for a project named demo-upload-csv-to-active-admin).

Once you are at the point of seeing the /admin route from that post, come back here to finish the rest.

The last things that we want to do:

# Create our "Template" model
$ bin/rails g model Template name:string description:string author:string

# Create a page for our CSV upload
$ touch app/admin/templates.rb

# Create a service folder for the CSV converter
$ mkdir app/services
$ touch app/services/csv_helper.rb test.csv

# Migrate changes for our template
$ bin/rails db:migrate
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At this stage, our project is now ready to start populating.

We will add some simple validations for our file app/models/template.rb here:

class Template < ApplicationRecord
  validates :name, presence: true
  validates :description, presence: true
  validates :author, presence: true
end
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Our CSV data will map to our name, description and author columns respectively.

"POST A","DESCRIPTION A","AUTHOR A"
"POST B","DESCRIPTION B","AUTHOR B"
"POST C","DESCRIPTION C","AUTHOR C"
"POST D","DESCRIPTION D","AUTHOR D"
"POST E","DESCRIPTION E","AUTHOR E"
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The idea is that each row will end up populating the data.

In app/admin/templates.rb, we will register a page "Template":

ActiveAdmin.register_page 'Template' do
  action_item only: :index do
    link_to 'Upload CSV', action: 'upload_csv'
  end

  page_action :upload_csv do
    render 'admin/csv/upload_csv'
  end

  page_action :import_csv, method: :post do
    templates = CsvHelper.convert_to_templates(params[:dump][:file])
    Template.transaction do
      templates.each(&:save!)
    end
    redirect_to({ action: :index }, notice: 'CSV imported successfully!')
  rescue StandardError
    redirect_to({ action: :index },
                flash: { error: 'CSV imported failed! Check the template is correct or contact a developer.' })
  end
end
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There are a few things that we are doing here:

The last action is most important. It will attempt to convert our CSV file to Template instances and then a transaction will attempt to upload them to the database (which we will also create soon).

If successful, the user will be redirected back to /admin/template with a success banner message displayed.

If the user is unsuccessful, the user will be redirected back to /admin/template with a failure banner message.

Next, let's tackle the view.

Create the file app/views/admin/csv/upload_csv.html.erb and add the following:

<%= form_for :dump, :url=>{:action=>"import_csv"}, :html => { :multipart => true
} do |f| %>
<table>
  <tr>
    <td>
      <label for="dump_file"> Select a CSV File : </label>
    </td>
    <td><%= f.file_field :file %></td>
  </tr>
  <tr>
    <td><%= submit_tag 'Submit' %></td>
  </tr>
</table>
<% end %>
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The above code will create a form that allows for a file, then on submission uploads that to the /admin/template/import_csv route that we have our handler for.

Finally, we need to add in the CsvHelper class.

Under app/services/csv_helper.rb, add the following:

class CsvHelper
  class << self
    def convert_to_templates(csv_data)
      templates = []
      csv_file = csv_data.read
      CSV.parse(csv_file) do |row|
        name, description, author = row
        templates << Template.new(name: name, description: description, author: author)
      end
      templates
    end
  end
end
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Here we are adding a class method to the CsvHelper class. This method takes CSV data from the upload, converts each row to a Template instance, pushes it to an array of templates and finally returns it.

The returned templates will start a transaction for them to be inserted (as you can see in the previous code for the form submission handler).

At this point, we can get to our admin panel and test things out.

Run bin/rails s to start the server, head to /admin and login with the admin@example.com and password details.

Once logged in, you can head to /admin/template and click on the Upload CSV link.

Template page

The following page will display the form for your CSV file upload.

Template form for the file upload

Once you select the test.csv file that we created, you will be redirected to the /admin/template/import_csv route with a success message (unless there is an issue).

Success

If you have an issue, you will see the error message:

Error

Today's post demonstrated how to upload a file to ActiveAdmin and process that upload.

Photo credit: bernardhermant